Aircraft components like flaps, spoilers, ailerons, rudders, elevators as well as intersecting components of an aircraft fuselage or wing structures require solutions with considerable out-of-plane strengths to withstand the loads introduced into the connected components. For example, in flaps the interface loads are usually introduced into ribs joined to a shell component of closed box structure of the flap body. Both of those structures are carrying loads predominantly in the main direction of the extension of the structures. Thus, in the intersection or connection regions of such structures, the planes of the force flows in each structure are intersecting as well.
This leads to specific load introduction requirements. Conventional composites produced by a ply-by-ply stack are usually not able to provide large out-of-plane strengths. On the other hand, isotropic materials like metal that are able to carry loads in three dimensions need to be provided with cut-outs, holes, vias or recesses in order to bolt or rivet them to intersecting components. In those cases, reinforcement measures need to be taken to maintain the structural integrity potentially leading to increased weight and manufacturing complexity.
Hitherto, several attempts have been made to improve the reinforcement of intersecting structural components. Document US 2010/0148008 A1 discloses a load introduction element of this type made of fiber composite material. Document DE 10 2009 043 103 A1 discloses a fiber composite structure comprising at least three fiber composite arms extending from a branching point. Document U.S. Pat. No. 4,715,560 A discloses a composite cruciform structure for joining intersecting structural members of an airframe of an aircraft. Document U.S. Pat. No. 4,586,226 A discloses a load transfer structure with intersecting webs formed of laminated sheets and fiber strands.